Police are investigating the online footprint of 15-year-old Abundant Life Christian School shooting suspect Natalie Rupnow -- who went by Samantha -- as they piece together the course of events that left three people dead, Rupnow among them.
Meanwhile, numerous schools in the Madison Metropolitan School District "were targeted by false threats often known as swatting" Tuesday, Madison Police Chief Shon Barnes told reporters at a news conference.
Police are investigating, Barnes said, and he noted authorities do not believe there are any current threats. "Making false threats is a crime, and we are working with the district attorney," he said.
Barnes said police are still working to establish a motive for Monday's deadly shooting, suggesting there were multiple factors.
Police are talking to students to determine if bullying was one, he said. "Everyone was targeted in this incident and everyone was put in equal danger," Barnes added.
Barnes said police are also investigating Rupnow's online activity. The police chief urged anyone who knew her or had insights into her feelings to call Madison Area Crime Stoppers at 608-266-6014.
One teacher and one student were killed in the Monday morning shooting, which took place inside a classroom during a study hall "full of students from multiple grade levels."
Two other students remain in critical condition with life-threatening injuries. Three students and a teacher suffered non-life-threatening injuries.
Rupnow died of a self-inflicted gunshot wound before law enforcement arrived, police said. Officers did not fire their weapons.
Rupnow's parents are cooperating with the investigation, Barnes told ABC News on Tuesday.
"They were cooperative. Despite this tragedy, they still lost a child. They still lost a member of their family," Barnes said.
"It is certain that they have probably more questions than anyone because they knew her," he said. "They lived with her and so we wanted to get an account from them of what kind of child she was."
Her father is being questioned by investigators, Barnes said. He said he didn't know whether the mother had been questioned, noting that she's been out of town.
A candlelight vigil was held Tuesday night at the state capitol for the victims of the shooting.
"Yesterday, the Madison community experienced a terrible and traumatic event," Madison Mayor Satya Rhodes-Conway said at the vigil. "We will never be the same, but we will get through this. And we will get through this together by relying on each other and taking care of each other."
The victims have not been publicly identified. Rhodes-Conway told reporters during the news conference that they are respecting the privacy of the victims' families and will "share what we can when we can and not before that."
"Let them grieve. Let them recover. Let them heal," she said.
Students in kindergarten through 12th grade attend the Christian school.
"I was in the hallway, and I was changing from my shoes to my boots to go to lunch because I have recess after, but then I heard the shooting and screams," a girl in second-grade told Chicago ABC station WLS.
James Smith told ABC News his 17-year-old daughter was in physics class at the time gunshots rang out two classrooms away. She wasn't hurt.
Smith said Abundant Life Christian School welcomes students who may have been bullied or had a tough time at other schools.
"We, as a school, desire to help those who are having troubles, to be able to provide a safe space for them to grow, at the same time balance across a safe space for the rest of our student body," he said.
Smith also said the school's population grew dramatically post-pandemic as many parents sought an alternative to public schools.
In the wake of Monday's shooting, President Joe Biden and Vice President Kamala Harris are urging elected officials to combat gun violence.
Biden in a statement called the shooting "shocking and unconscionable," and he mentioned his administration's efforts to combat the gun violence epidemic in the U.S., including the implementation of the White House Office of Gun Violence Prevention.
Biden asked Congress to pass "commonsense" gun safety laws, including universal background checks, a national red flag law and a ban on both assault weapons and high-capacity magazines.
"It is unacceptable that we are unable to protect our children from this scourge of gun violence," Biden said, adding, "We cannot continue to accept it as normal."
"It's another school shooting, another community being torn about and torn apart by gun violence," Vice President Kamala Harris said in remarks Tuesday. "And of course, our nation mourns for those who were killed, and we pray for the recovery of those who are injured and for the entire community."
Harris, who played a role in the Biden administration's efforts to combat gun violence, stressed, "We as a nation must renew our commitment to end the horror of gun violence, both mass shootings and everyday gun violence that touches so many communities in our nation."
"We must end it, and we must be committed to have the courage to know that solutions are in hand, but we need elected leaders to have the courage to step up and do the right thing," she said.